In recent years, an optical coherence tomographic imaging method and an optical coherence tomographic imaging apparatus, to which a low coherence interferometer technology or a white light interferometer technology is applied, are practically used.
In particular, an optical tomographic imaging apparatus that performs an optical coherence tomography (OCT) utilizing interference of multi-wavelength light can obtain a tomographic image of a sample with high resolution.
Therefore, in the ophthalmological field, an optical coherence tomographic apparatus is becoming an indispensable apparatus for obtaining a tomographic image of a fundus or a retina.
In addition to the ophthalmological application, the optical coherence tomographic apparatus has also been used for tomographic observation of skins, wall surface tomographic photographing of a digestive organ or a circulatory organ with an endoscope or a catheter constituted of the apparatus, or the like. Hereinafter, the optical coherence tomographic apparatus is referred to as an OCT apparatus.
The OCT apparatus utilizes characteristics of light to enable measurement with high resolution compared with an ultrasonic tomographic diagnosis apparatus or the like, and thus can perform fine measurement but requires a long measurement time for measuring a wide region.
In order to cope with the above-mentioned problem, there is known a method of using a plurality of measurement lights and deviding a wide region into a plurality of regions to be measured with the individual lights simultaneously.
Japanese Patent No. 2875181 discloses an optical coherence tomographic imaging apparatus, which uses a plurality of light sources and photosensors so that the individual light sources and photosensors are associated with each other by a common imaging optical system.
In addition, Japanese Patent Application Laid-Open No. 2006-195240 discloses an apparatus that splits one light into a plurality of condensed lights by a micro lens array so as to perform interference measurement.
In structuring the OCT apparatus using a plurality of lights, the following problems can occur, which are not examined in the above-mentioned conventional examples disclosed in Japanese Patent No. 2875181 or Japanese Patent Application Laid-Open No. 2006-195240.
Specifically, in structuring the OCT apparatus using a plurality of lights, the individual lights actually follow different optical paths. Therefore, influence of an optical system including an optical path length, light quantity, wavelength dispersion, aberration and a signal processing step are different among the individual lights.
These factors cause variations of contrast, resolution, sensitivity, and the like in OCT images obtained by the individual lights, and hence it is necessary to reduce the variations.
In order to reduce the variations, it is necessary to equalize the influence on the individual lights, which increases the number of components and cost in proportion to the number of lights.